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June 25, 1991 ARCO Service Station 760, Lodi, California Org June 18, 1991, we collected soil samples S-13-Ti through S-13-T3 from beneath the north and south ends of the former tanks at 13 feet below grade. Two soil samples(S-6-1N and S-10-2N) were collected from the north sidewall to evaluate residual hydrocarbon concentrations remaining in the soil. One sample was collected from the south sidewall(S- 10-1S) to delineate soil with residual hydrocarbons in that direction because a soil boring was not drilled at the southern end of the tank cavity during the October 1990 investigation. Soil samples were also collected in the proposed tank cavity at 12 feet below grade(samples S-12-T4 through S-12-717). On June 19, 1991, a 550-gallon waste-oil tank was discovered during excavation of the proposed tank cavity(la5eled tank T8 on Plate 2). We collected a sample of the liquid from inside the tank (W-6-T8). On June 21, 1991, soil samples S-12-T6 and S-12-T6S were collected from approximately 12 feet below grade at the northern and southern Iimits of the proposed tank cavity. Tank T-8 was also removed on that date, and a soil sample (S-12-T8) was collected from 12 feet below grade under the former tank. Laboratory Analyses Soii samples collected under tanks T1 through T3 were analyzed for total petroleum hydrocarbons as gasoline(TPHg) using Environmental Protection Agency(EPA)modified Method 8015,benzene, toluene, ethylbenzene,and total xylene isomers(BTEX)using EPA Method 8020, 1,2,-dibromethane(EDB)using EPA Method 8240, and total lead using EPA Method 6010. Soil samples collected from the bottom of the proposed lank. cavity were analyzed for TPHg and BTEX. The soil sample collected under lank T-8 was analyzed for TPHg. BTEX, total petroleum hydrocarbons as diesel (TPHd) using EPA' vlethod 8015, total oil and grease(TOG)using Standard Method 5520e and f,volatile organic compounds (VOC's)using EPA Method 8010, and total metals using EPA Method 6010 for cadmium, chromium III,chromium VI,nickel, lead and zinc. Copies of the Chain of Custody Record and laboratory reports are attached to this letter. Laboratory Resins Results of analyses of the soil samples collected under former tanks TI through T3 and the sidewalls of the former tank cavity are presented in Table 1. Residual hydrocarbon concentrations remaining in place in the former tank cavity range from 0.52 to 250 parts per million TPHg and from 0.01 to 18 ppm BTEX. Concentrations of EDB and total lead were b?low detection limits. 0624 irc 38048-5 2 r